// Physical memory allocator, for user processes,
// kernel stacks, page-table pages,
// and pipe buffers. Allocates whole 4096-byte pages.

#include "types.h"
#include "param.h"
#include "memlayout.h"
#include "spinlock.h"
#include "riscv.h"
#include "defs.h"

void freerange(void *pa_start, void *pa_end);

extern char end[]; // first address after kernel.
                   // defined by kernel.ld.

struct run {
  struct run *next;
};

/*
  现在只有一个唯一的空闲内存链表
*/
// struct {
//   struct spinlock lock;
//   struct run *freelist;
// } kmem;

struct {
  struct spinlock lock;
  struct run *freelist;
} kmem[NCPU];

void
kinit()
{
  // initlock(&kmem.lock, "kmem");
  // freerange(end, (void*)PHYSTOP);

  for(int i = 0; i < NCPU; i++) {
    char lock_name[10];
    if(snprintf(lock_name, sizeof(lock_name), "kmem%d", i) == 0) {
      panic("kinit");
    }
    initlock(&kmem[i].lock, lock_name);
    kmem[i].freelist = 0;
    if(i == 0) // 注意这里，内存一定不能重复进行分配！！！该操作系统中对此没有任何的检测
      freerange(end, (void*)PHYSTOP);
  }

  for(int i = 0; i < NCPU; i++) {
    printf("CPU%d: %p\n", i, kmem[i].freelist);
  }
}

void
freerange(void *pa_start, void *pa_end)
{
  char *p;
  p = (char*)PGROUNDUP((uint64)pa_start);
  for(; p + PGSIZE <= (char*)pa_end; p += PGSIZE)
    kfree(p);
}

/*
  这个函数的函数传参是不能修改的，因为还有其它文件中的内容使用了该函数
*/
// Free the page of physical memory pointed at by pa,
// which normally should have been returned by a
// call to kalloc().  (The exception is when
// initializing the allocator; see kinit above.)
void
kfree(void *pa)
{
  push_off();
  int index = cpuid(); // 获取CPU的id
  pop_off();

  struct run *r;

  if(((uint64)pa % PGSIZE) != 0 || (char*)pa < end || (uint64)pa >= PHYSTOP)
    panic("kfree");

  // Fill with junk to catch dangling refs.
  memset(pa, 1, PGSIZE);

  r = (struct run*)pa;

  acquire(&kmem[index].lock);
  r->next = kmem[index].freelist;
  kmem[index].freelist = r;
  release(&kmem[index].lock);
}

// Allocate one 4096-byte page of physical memory.
// Returns a pointer that the kernel can use.
// Returns 0 if the memory cannot be allocated.
void *
kalloc(void)
{
  push_off();
  int index = cpuid(); // 获取CPU的id
  pop_off();

  // printf("the index is%d\n", index);

  struct run *r;

  acquire(&kmem[index].lock);
  r = kmem[index].freelist;
  if(r)
    kmem[index].freelist = r->next;
  release(&kmem[index].lock);

  int i = index + 1;
  while(r == 0 && i != index) {
    if (i >= NCPU) {
      i %= NCPU;
      continue;
    }

    acquire(&kmem[i].lock);

    r = kmem[i].freelist;
    if(r) // 有可用的
      kmem[i].freelist = r->next;

    release(&kmem[i].lock);

    // printf("%p ", r);
    i++;
  }
  // printf("\n");

  if(r)
    memset((char*)r, 5, PGSIZE); // fill with junk
  return (void*)r;
}